The 1991 Plymouth Sundance with the 2.5L I4 is a basic commuter from Chrysler's K-car era that suffers from chronic head gasket failures and transmission cooler line leaks, plus typical late-80s electrical gremlins. Budget-friendly when running, but major engine work often exceeds the car's value.
Head Gasket Failure (2.5L I4)
Common · high severityTypical onset: 80,000-140,000 mi
Symptoms: white smoke from exhaust, overheating without obvious coolant leak, oil milkshake on dipstick, bubbling in coolant reservoir at idle
Fix: Head gasket replacement requires 6-8 hours labor; machine shop resurface typically needed ($80-120). Often find cracked head on high-mileage examples requiring replacement head ($200-400 core). Smart shops pressure-test before reassembly.
Estimated cost: $800-1,400
Automatic Transmission Cooler Line Leaks
Common · medium severityTypical onset: 70,000-110,000 mi
Symptoms: transmission fluid puddles under radiator area, burnt transmission smell, slipping between gears, low fluid without visible pan leak
Fix: Steel cooler lines rust through at crimp points and radiator connections. Line replacement is 2-3 hours; often discover internal radiator cooler has failed, contaminating trans fluid with coolant (requires trans flush or rebuild). Always replace both lines and inspect radiator cooler integrity.
Estimated cost: $300-600 for lines only; $1,200-2,200 if trans damaged
Crankshaft Position Sensor Failure
Common · high severitySymptoms: no-start when hot, restarts after cooling 20-30 minutes, intermittent stalling at operating temperature, cranks but won't fire, no check engine light on early failures
Fix: Hall-effect sensor behind timing belt cover fails from heat cycling. Requires timing belt cover removal, 1.5-2 hours labor. Sensor is $40-80. Classic failure mode: dies in parking lot, restarts after grocery shopping. Scanner may not set code until complete failure.
Estimated cost: $150-280
Front Seat Recliner Mechanism Breakage
Occasional · medium severitySymptoms: driver seat back suddenly reclines without warning, recliner lever feels loose or disconnected, seat back won't lock in upright position
Fix: NHTSA recall component; internal recliner pawl breaks, especially driver side from repeated use. Used seat from salvage yard is 1 hour swap. New mechanisms NLA from dealer; aftermarket rebuilds available but quality varies. Safety issue if fails while driving.
Estimated cost: $180-350
Fuel Pump Relay and ASD Relay Failures
Occasional · high severitySymptoms: intermittent no-start, no fuel pump prime sound, stalling after warmup, won't start until you wiggle relay under hood, loses power while driving, restarts immediately
Fix: Relays in power distribution center fail from heat and corrosion. Both fuel pump and Auto Shutdown (ASD) relays should be replaced together (0.5 hour labor). Carry spares in glovebox—common roadside failure. Relays are $15-25 each. Also clean relay socket terminals with contact cleaner.
Estimated cost: $80-150
CV Axle Boot Tears and Joint Failure
Common · medium severityTypical onset: 60,000-100,000 mi
Symptoms: clicking during turns, grease splatter on wheel wells, vibration during acceleration, torn rubber boot visible on axle
Fix: Outer CV boots tear first, allowing grease loss and contamination. Reboot is 1.5 hours per side if caught early; most shops replace entire axle (2 hours per side) for $60-90 reman unit rather than rebuild. Do both sides if one fails—the other is close behind.
Estimated cost: $220-400 per axle
Buy only with documented head gasket replacement and for under $800; engine work quickly exceeds the car's total value and parts availability is declining fast.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.